1. Field of the Invention
This invention relates to a polishing apparatus to be suitably used for the process of preparing a wiring section of a semiconductor device such as a semiconductor memory, which may be a DRAM, or a microprocessor and that of an electrooptical device such as a liquid crystal device or a plasma display device. It also relates to a polishing/cleaning method to be used with such an apparatus as well as to a method of preparing a wiring section.
2. Related Background Art
Firstly a known process of preparing a wiring section of a semiconductor device will be described.
The technique of CMP (chemical mechanical polishing) has been widely used in recent years in the process of manufacturing semiconductor devices and electrooptical devices in order to alleviate the problem of the depth of focus that can arise in the exposure step of photolithgraphy and improve the step coverage of the coat of the device.
FIGS. 14A through 14D of the accompanying drawings are schematic cross sectional side views of a semiconductor device, illustrating different manufacturing steps.
A silicon oxide film 102 is formed by plasma CVD on a semiconductor wafer 100 carrying thereon lower wires 101 that are made of polycrystalline silicon or silicide and operate as components such as gate electrode. The surface of the produced silicon oxide film may show projections and recesses due to the underlying wires 101 (Step PAS1, FIG. 14A).
Then, the surface of the silicon oxide film is polished by means of a polyurethane polishing pad and a polishing agent prepared by dispersing fine silicon oxide particles in an aqueous solution of KOH until the surface becomes flat (Step PAS2, FIG. 14B).
Subsequently, the work is cleaned by means of an acidic or alkaline chemical agent and a brush. Then, photoresist is applied to the surface of the flattened and smoothed silicon oxide film and expose the photoresist to a beam of KrF excimer laser to produce a latent image of the pattern for forming a contact hole. Thereafter, the latent image is developed to produce a photoresist pattern. The work is then subjected to RIE (reactive ion etching) by using the patterned photoresist as mask to produce a contact hole 103 (Step PAS3, FIG. 14C).
Thereafter, the photoresist is removed and a silicon-containing aluminum film 105 is formed in the contact hole and on the silicon oxide film (Step PAS4, FIG. 14D).
A multi-wire arrangement can be obtained by repeating the above process.
However, it has recently been found that some of the substances that have adhered to the semiconductor device during the manufacturing process cannot be removed by the above described cleaning method.
For example, a polishing agent obtained by dispersing fine particles of silicon oxide in a potassium-containing treatment agent such as an aqueous solution of potassium hydroxide (KOH) may be used in the above described CMP process. However, the potassium (K) that have adhered to the interlayer insulation film to be polished out of the polishing solution cannot be removed by a chemical cleaning solution of aqueous hydrogen peroxide containing sulfuric acid or ammonium. Nor was it possible to remove it by means of a brush.